1. Field of the Invention
This invention relates generally to an underwater erosion control system, and in particular, to an underwater erosion control system that disrupts laminar flow and increases viscous drag to cause particulates in fluids to precipitate.
2. Description of the Related Art
Devices used to prevent erosion of underwater surfaces, such as riverbeds, seabeds, and the like, and cause particulate deposition are known. Typical devices include buoyant frond elements or artificial seaweed anchored underwater in the area in which bed erosion (i.e., sea floor scour) is to be prevented. These devices operate by increasing viscous drag on the underwater current, which reduces the velocity of the current and of particulate transported by the current to a level where the particulate settles out of the current and is deposited in and around the erosion control system.
For example, U.S. Pat. No. 5,176,469 to Alsop discloses a structure comprising a continuous sequence of buoyant fronds arranged side by side to form a frond line. The frond line is folded back and forth to form frond sections. Each section has an aligned opening for receiving an anchor line for anchoring the array to the sea bed.
Another example of an underwater soil erosion prevention system is shown in U.S. Pat. No. 4,722,639 to Alsop. In this system, an open grid mat structure is used as a base to attach a number of randomly overlapping elongate buoyant frond elements. The open grid mat structure requires the grid lines to be at least nine inches (9") apart from one another in practice. Spacing the grid lines, and thus frond elements, so far apart from one another limits the viscous drag exerted and the amount of disruption of laminar flow on the current, and thus, the structure's erosion prevention capabilities. In addition, the open grid mat disclosed in the foregoing patent is not adapted to be efficiently manufactured and deployed.
An additional problem with prior underwater erosion prevention and control systems is the inability to provide a strong and durable yet sufficiently buoyant system to form a mound or berm of particulate removed from suspension. The system must be strong enough to provide sufficient resistance to the water current and durable enough to sustain resistance to the water current for an extended period of time. The system must also be sufficiently buoyant to rise to a level to be effective in dissipating enough energy in the moving fluid to cause particulate deposition and formation of a berm appropriate to arresting the erosion.
Therefore, a need exists for an easily manufactured and deployed device with sufficient durability and buoyancy to exert a maximum amount of laminar flow disruption and viscous drag on the water flow to maximize erosion control.